Process and apparatus for cracking hydrocarbon oils



Oct. 5 1926. 1,601,728

I W. F. FARAGHER ET AL PROCESS AND APPARATUS vFOR CRACKING HYDROCARBON OILS Filed Jan. 15, 1921 2 Sheets-Sheet 1 Oct. 5, 1926. 1,601,728

W. F. FARAGHER ET AL PROCESS AND APPARATUSFOR CRACKING HYDROCARBON OILS Filed Jan. 15, 1921 2 sheets-sheet 2 'HHIIII'... 11m.

IIIII'IIIHIH @51 1 W abtozwew PM $9M M X avwemtoz:

Patented Oct. 5, i926.

UNITED STATES PATENT OFFICE.

, WARREN F. FARAGHER, WILLIAM ARTHUR GRUSE, AND FREDERIC HORACE GARNER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO GULF REFINING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF TEXAS.

PROCESS AND APPARATUS FOR CRACKING .HYDROCARBON OILS.

Application filed January 15, 1921. Serial No. 437,482.

to improvements in the cracking of such oils in a st1ll of the horizontal cylindrical boiler type of the classreferred to in our copending applications Serial l los.-l37,48 1v and 628,501.

When such oils are subjected to crack ng in an externally heated still, serious dlfliculties are encountered'in large-scale operations, due to the deposition of a carbonaceous solid, commonly referred to as carbon, on the heated walls of the still. Such a deposition of carbon interferes with the conduction of heat into the oil, and results in increased cost of gasoline-production owing to the necessity of cleaning the carbon from the still-walls and the loss of operating time during such cleaning operations; while the life of the. still-wall is comparatvely short due to the rapid burnout of the iron in contact with carbon.

Attempts have been made to overcome the difliculties mentioned by providing stirrerS in the. still for agitating the oil, but such stirrers are open to the objection that they require stuffing boxes which must operate against highly heated oil or hot oil vapors at high pressures.

According 'to the present invent-ion, the

' cracking operation is carried out ina still of the horizontal cylindrical boiler type, but with avoidance or substantial avoid: ance of objectionable deposition of carbon on the still walls, and with efiicient circulation of the oil 'in the still, without the provision of mechanical stirrers.

In carrying out the invention, we provide, in a horizontal boiler type of still, a 1plurality of transversevvertically arranged aflles, extending acrossthe still and spaced apart from each other and from the bottom of the still, and dividing the oil into a series o-l transverse bodies, and we provide for the introduction of jets of gas between certain of the baflles so as to bring about an effective circulation of the oil, upwardly between certain of the baflles and downwardly between certain of the other battles.

the individual spaces of the series.

The alternate spaces between the bafiles, into which the gas is introduced and through which the 'oil is caused to flow upwardly, may be sub-divided, by artitions, into a series of spaces, arrange as a transverse series, and the gas introduced into eachTplf e bafiies. extend to near the heated bottom of the still and upwardly to near the top" of the body of oil therein, or to a suflicient I height so that the currents of gas introduced therebetween will bring about effective circulation of the oil over the heated bottom of the still, and so that the forms. tion of an objectionable dead layer of oil on the heated bottom bf the still is avoided. The resulting circulation of the oil in'a series of circuits 01'- cycles along the length of the still brings about effective and uniform heating and circulation of the entire body of oil inthe still and promotes the desired crackin operation.

The still itse f, as well as the construetion, arrangement and number of transverse baflies, can be varied, and the still can be operated intermittently, upon successive invention and adapted for the practice of the process of the invention.

In the accompanying drawings Figs. 1 and 2 show one embodiment of the apparatus in vertical transverse section, and vertical longitudinal section, respectively, Fig. 1 being asection on line 1-1 of Fig. 2 and Fig. 2 being a section on line 22 of Fi 1;

Fig. 3 sliows a modified form of apparatus, in transverse sectionon line 3' -3 of Fig. 4.; v I r Fig. d is a partial, vertical, longitudinal section on line 4 4 of Fig. 3; and

Fig. 5 is a partial, vertical, longitudinal. section of a further modified construction of the apparatus. i

In the different figures of the drawings similar parts are indicated by the same reference numerals with the letters a or b appended thereto in Figs. 3, i and 5.

In the apparatus illustrated in Figs. 1 and 2, the still 1 is an ordinary horizontal cylindrical boiler type of still with its bottom arranged in a furnace chamber 2 so that it will be heated by direct heat or by products ofcombustion. The furnace structure and the particular method of heating can, of course, be varied. The still is provided with the usual oil inlet pipe 3 from which oil is supplied in any suitably regulated manner, with the vapor outlet 4C from which the vapors are led successively to a dephlegmator' and condenser (not shown), and the residue outlet 5. It will be understood that the oil can be supplied in a more or less continuous manner, and the oil supply re ulated automatically in accordance with tie desired level to be maintained in the still, where the operation is to be carried out in a continuous manner. So also, the residue can be withdrawn periodically or continuously. A particu-" larly advantageous arrangement of the oil inlet and residue outlet is to have these at having a suitable regulating va ye there- In the apparatus of Figs. 3 and 4, the

transverse directing battles are inclined and.

made narrower at their upper ends in order to reduce the speed of gas separation and assist inmaintaining the foam in the still. In the apparatus of Fig. 5 the directing bafties are curved and nearer together near their central or intermediate portion, giving a section similar in appearance to that of a Venturi tube. l l 1 As above stated, the transverse spaces through which the oil is circulated up wardly by theintroduction of the gaseous currents (acting on the air-Iift principle), may be sub-divided by partitions into a series of small spaces, into each of which the gas is introduced to bring about the airT-lift circulation. Such an arrangement is illustrated in Figs. 3 and 4, and also in Fig. 5, in which a series of partitions 12 and 12 respectively, are provided, forming a series of transversely arranged spaces. Each mamas of the spaces thus formed is provided with one or more gasjets, shown as short branch pipes 18 in Figs. 3 and 4, extending upwardly from the gas supply pipes 7 and 8. The battles 1% near the side walls of the still may be somewhat curved to'conform to the contour of the still walls and leave a space between them and the still walls which is not materially greater in cross section at the top than at the the bottom. So also, the end jet pipes 15, through which' the gas jets are introduced, may be arranged to discharge outwardly and upwardly, as shown, in order to promote the circulation of the oil through these outer individual spaces. The intermediate spaces between the transverse-battles, through which the oil flows downwardly, are left free and unobstructed, in the apparatus illustrated in Figs. 3 and 4..

In Fig. 5 the supply pipe 8 for the gas is so arranged that the gas jets discharge therefrom, for example, through branch tubes 16, arranged at the narrowest portion of the space between the bafies, to increase the resulting jetting action and thereby promote the circulation.

in the operation of the apparatus, the oil 7 is maintained therein at a suitable level by suitable automatic or other regulating means (not shown), and the still is heated from below in much the usual way. Currents of gas are forced in through the various branch pipes and rise upwardly in the oil between the baffles, thus causing an upward circula tion of the oil between the battles and a downward flow of oil between the alternate pairs of battles which have no gas jets between them. Circulation is thus brought about in a series of paths or cycles, each path or cycle involving the downward circulation of the oil between the baffles, the flow of the oil underneath the lower edges of the baflles, and the upward flow of the oil in the alternate spaces between the battles due to the gas introduced therebetween, acting on the air-lift principle. The oil is thus kept effectively agitated and circulated, while the bottom of the still which is subjected to the direct heat of the furnace chamber is kept substantially free from objectionable carbon deposit by the scouring "action of the rapidly circulating oil which forms scouring eddies in its flow beneath the lower edges of the baffles. The entire body of oil in the still is thus broken up into a series of smaller circulating bodies which circulate in the manner above described, ,ina series of cycles around the vertical transverse battles.

When the oil inlet is at one end of the still and the residue outlet is at the other, it will be seen that the oil flowing through the still from the inlet to the residue outlet tends to pass progressively along the still where it is recirculated in the successive cycles. By properly proportioningthe height of the to undergo recirculation in theseries of paths around the successive baflies. The circulating of oil tends to scour oil any carbon deposit that may form on the heated surfaces and its scouring action is promoted by the carbon that maybe carried in suspension in the oil during its circulation. Thus, even if a considerable accumulation of carbon is present in the oil near the residue discharge end of the still, the effective breaking up of the oil into a series of successive circulating bodies, and the rapid and effective circulation, keep the carbon in suspension and prevent it from forming objectionable carbon deposits on the heated bottom of the still.

The gas which is used for bringing about the circulation of the oil in the manner described maycadvantageously be a part of they fixed gases or of the vapors produce by the cracking'operation itself, but other appropriate gas can be used, such as natural'gas or casing-head gas, or other gaseous material such as steam, which has no Tobjectionable'etfect upon the cracking operation. The fixed gas from the condenser may thus be returned to the still for bringing about the circulation, or a partof the hot gases and admixed vapors may be taken from the vapor line leading to the final condenser and returned to the still for this purpose. wIlfthe condenser is operated under the same pressure as the still, as in the preferred practice, the fixed gas can bewithdrawn at this pressure and recirculated so that the amount of further compression necessary is correspondinglyfieduced. So also, if a part of the hot gases and vapors are taken oil at some point between the still and the final condenser, and reintroduced into the still, their heat will be to a. considerable extent conserved: The gas that is introduced intocthe stillcan itself be preheated to avoid the coolin effect that might otherwise'be objectiona 1e.

The introduction of the currents of gas I not only serves to insure effective agitation and circulation'of the oil, but it promotes the regular removal of the lower boiling.

constituents resulting from the cracking. op= eratlon as they are formed, and prevents their "remaining in the still for prolonged periods of time'to'undergo further decomposition. The gases and va ors produced by the cracking operation Wlll be diluted by the gases separately introduced and the entire mixture will he passed through the dephlegmator and vapor pi e to the condenser or condensers for t e removal of condens1ble const1tuents. The excess gas can be discharged in any suitable manner.

If apart of'this gas is to be used for reintroduction into the still, through a pump or gas booster and brought to the necessary pressure for its reintroduction; It will be understood that the pressure of the gas can be Varied, and that the rapidity of circulation and violence of agitation of the oil can be to a certain extent controlled by the rate and pressure of the g'asintroduced, as well as by the arrangeit. can be passed v ment of the gas inlet pipes and of the baflfles in the still.

In carrying out the process, it will be understood that the, oil is raised into that range of temperature in which cracking occurs, and maintainedat the appropriate temperature and pressure for the cracking operation. 7 The rapid and elficient circulation of the oil and the breaking up of the oil body'into a series of locally circulated portions, tends to prevent any local objectionable overheating of any portion of the oil and permits the uniformity of heating d of the entire body of oil so that the operation can be carried out with the production of considerable amounts of naphtha and gasoline and relatively little gas and carbon, and without objectionable local overheating of the oil to the still higher temperature at which much gas and-carbon are formed. The'continuous and effective circulation of the oil keeps the entire body of oil in the desired temperature range and gives a resulting cracking operation of a more uniform character. The oif which becomes hot by its circulation in contact with the'heated bottom of the still is continuously swept or scoured off so that the formation of a deadlayer of oil is prevention of the heating of such a layer to objectionably high temperatures, and hence with substantial avoidance .of objectionable carbon deposit. Much more prevented, with resulting effective heat transfer through the heated:

bottom of the still is thus made possible,

while the still bottom itself is protected by the absence of any objecionable layer of carbon deposited thereon such as is common in horizontal boiler stills as they are now operated.

It will be seen that the entire circulation of the oil, is brought about by the arrangement of the baffles and the introduction of the gaseous currents, acting on the air-lift" :principle, so that mechanical agitators and pressure.

"'- ing pressure of, for

sure and temperature indicating devices, as

well as suitably regulated oil supply means, which may be automatic, for maintaining a regulable oil supply and oil level in the still and suitable means for supplying the gas in sutiicientamount and under an appropriate Temperature indicating devices can thus be provided between successive or alternate bellies, along the length of the 'still, so that the operator can t ll the temperature of the oil circulating in different parts of the still and be warned of any irregularity of operation. 'The condenser (not shown) may be of any suitable construction, and, in the preferred practice, is in open communication with the still and -opcrated at the still pressure, with the regulating valve in the line beyond the condenser. 'lhe condenser can, however, be operated at a lower pressure, and a suitable regulating valve provided between the still and con denser for this purpose. A regulated crackexample, between and 500.1bs. per square inch, and preferably in the neighborhood of to 159 lbs; per square inch, can thus be maintained, the temp ature and pressure varying some, hat with the nature of the oil to be cracked and the products desired.

'lhe oil feed to the still may be preheated to a greater or less extent, and, nis purpose, a part of t e necessary heat can be supplied by means of a heat interchanger {not shown) through which the still hotterms are discharged; while apart of the preheating maybe etl'ected by bringing the oil into heat-interchanging relatio with. the hot vapors from the still. The oil feed can thus be passed through the condenser for the vapors from the still, or through one or more of the series of such condensers wher such a, series is used for cooling and condens ing the vapors. The preheating eilect thus,-

a secured may be supplemented, if desired,

further preheating of the oil feed in suitable manner, and the oil can advantageously be preheated to such a degree as to vaporize and remove any water present therein before the oil is introduced into thestill.

t will thus be seen that the present invention providesfor the carrying out of the cracking operation with eifilective circulation tenures and recirculation of the oil in a particularly advantageous manner which promotes and insures uniformity of circulation and of heating of the entire body of oil as well as the prevention or substantial prevention of objectionable carbon deposit upon the heated still bottom. The erosive action of the oil upon deposits on the still bottom can be further increased by adding to the oil a lit tle sand, fine gravel or metal filings, which are circulated with the oil and assist in preventingand removing objectionable carbon deposition.

in referring to the cracking of oil in the present specification and claims, we intend to include the treatment of various hydrocarbon oils and more particularly the treatment of higher boiling fractions and residual oils of petroleum or shale oil distillation, for the production of motor fuel or gasoline; but other oils, such as lignite or coal tar, or vtar oils, etc., can be similarly treated; and we include all such materials within the term oil, as used in the accompanying claims.

t is to be understood that a plurality of stills of the-designs disclosed in this specification may be arranged in series and the oil to be cracked passed through them consecutively,

We claim:

The method of cracking oils in a horizontally arranged still, which comprises. heating a body of the oil therein by external heat to the cracking temperature under pressure, subdividing the main body of oil in the still into a series of transversely arranged smaller bodies communicating with each other at their upper and lower ends, introducing the oil .to be cracked at one end of the still and withdrawing the residue from the other, and maintaining eifective circulation of thebil in the said transversely arranged bodies and along the heated bottom of the still by the introduction of gaseous current-s, acting on the air-lift principle, near the lower ends of the sub-divided smaller bodies 2. in apparatus for cracking oils, comprising a horizontally arranged and externally heated still having a series of vertically arranged transverse battles therein'spaced apart from the still "bottom and means for introducing gaseous currents into the alternate spaces between the baffles, whereby circulation of the oil is ellectedaround the said baffles and over the bottom of the still,

3. An apparatus for cracking oils comprising a'horizontally arranged and externally heated still having an inlet at one end and a residue outletat the other, a series of transversely arranged bafilesin the still bring about effective circulation of the oil in the still.

4. An apparatus for cracking oil comprising a horizontally arranged and externally 5 heated still having an oil inlet at one end and a residue outlet at the other, a series of Vertically arranged transverse bafiles Within the still spaced apart from the still bottom,

and means for introducing upwardly flowing gaseous currents into the alternate spaces 1 between said baffles.

In testimony whereof We aflix our signatures.

lVARREN F. FARAGHER.

lVILLIAM ARTHUR GRUSE.

FREDERIC' HORACE GARNER. 

